We propose to study the long term regulation in brain of the enzyme choline acetyltransferase (CAT), the enzyme catalyzing the biosynthesis of the neurotransmitter acetylcholine. Moreover, since the enzyme exists in multiple forms (isozymes), we shall investigate whether the different forms are regulated together or independently. To accomplish this we shall: 1. purify and prepare antibodies to the different forms of CAT from rat brain; 2. analyze regionally in brain the molecular basis of the different forms; 3. characterize the kinetic parameters and specific catalytic activity of each form; 4. determine their turnover rates; 5. establish if the enzymes can be induced (more enzyme molecules) or activated (increased catalytic activity/molecule) by psychoactive drugs, by brain lesions and during growth and development.